In this paper we present the standard Thomistic view concerning substances and their parts. We then note some objections to that view. Afterwards, we present Aquinas’s Christology, then draw an analogy between the relation that holds between the Second Person and the assumed human nature, on the one hand, and the relation that holds between a substance whole and its substance parts, on the other. We then show how the analogy, which St. Thomas himself drew at points, is useful for (...) providing a theory that answers the objections that the standard Thomistic view faces. Finally we answer objections to our approach. We conclude that there is a hylomorphic theory, founded on an analogy from Aquinas’s Christology, that fits well with the empirical data concerning substance parts, on which some complete created material substances have other complete created material substances as parts. (shrink)